1. Field of the Invention
This invention is directed to the field of hydraulic actuators, and more particularly, to an in-line hydraulic dashpot that substantially noiselessly decelerates a hydraulic power cylinder at any selected point of its power stroke.
2. Description of the Prior Art
Existing power cylinders are designed with a cup and cone dashpot built into either one or both ends of the power cylinder. The cone is normally a portion of the power cylinder's piston, while the cup is normally built into the end cap of the power cylinder.
For the principal portion of the stroke's length of travel, these pieces have no effect either on the speed or on the operation of the power cylinder itself. But, as the power cylinder approaches its end of travel, the cone starts to enter the cup.
The cone and cup are complementarily tapered. As the cone successively enters the cup, the amount of clearance between the two pieces continually decreases. As a result of the smaller and smaller exit area available for the oil or other hydraulic fluid to get out of the decreasing cup and cone cavity, the fluid builds an ever increasing pressure. This increasing pressure results in a force which resists the piston as it is being driven into the cup and slows the piston down so that when it reaches its end of stroke, its velocity has decreased to an extent that the mechanical impact, and hence noise, is minimized at the end of stroke.
Among the problems associated with the cup and cone dampers of the heretofore known power cylinders is the difficulty in providing consistent simultaneous cup/cone occurrence at the end of travel of the stroke of the piston of the power cylinder. Such could be caused to occur when the power cylinder is first installed by the proper positioning of the power cylinder with respect to the installation of the mechanism which is driven by the power cylinder, although such adjustment becomes disadvantageous to the extent that any change in the mechanism driven by the power cylinder, as caused by wear, system deflections, or the replacements of other parts of the total system, could result in the need to adjust the end of stroke of the power cylinder in a direction where no adjustment was in fact available. To accommodate such changes, it has been the practice heretofore to install the power cylinder so that the piston did not bottom out at the end of stroke. Although this provided the capability to adjust, if and as necessary, the final position of the piston at a later date, it paid the penalty of reducing the effectiveness of the power cylinder's cup and cone dashpot.